The doctors who signed the open letter, led by David Nicholl, a neurologist at City Hospital in Birmingham, want to see Hospira following the example of Lundbeck, the Danish manufacturer of a barbiturate called pentobarbital that has been also used in US executions.

Lawyers for death row inmate Gregory Walker argued that recording DeYoung's execution would provide critical evidence in his appeal about the effects of pentobarbital, which is the sedative now being used as the first step in Georgia's injection procedure.

Lundbeck, which manufactures the drug in the US under the tradename Nembutal, now demands that its US distributors sign an agreement stating that they will not make pentobarbital, which is a sedative with a wide range of uses, available for prisons using it for lethal injections.